Avian influenza, first identified in Italy more than 100 years ago, affects birds. Migratory wildfowl, particularly wild ducks, are the natural reservoir. As with many animal diseases, humans can sporadically become infected under special conditions. Eighteen people were infected and six died during the outbreak of avian influenza (H5N1) in poultry in 1997. Since that time, the H5N1 virus has spread to several Asian countries affecting domestic chickens and ducks. The virus was recently found in migratory birds in Europe and further spread is likely.  Furthermore, sporadic transmission of the H5N1 virus in humans has taken place in the affected countries. The major concern about avian influenza is that it could combine with human influenza viruses and develop into a new strain of human influenza that could spread person to person.